DeskClock : Improve the priority of power off alarm broadcast

If device power off before power off alarm action is received, power
off alarm value will not be set to rtc. Then this function will not
work. So set power off alarm broadcast to foreground action to make
it be received in time.

CRs-Fixed: 2075052
Change-Id: I6750565396fc79d98e102d2e6515963f3ef978c8